The invention relates to a gas generator for an airbag module.
For the activation of airbags gas generators are known which have a propellant with an ignition device in a gas generator housing. The propellant is arranged in a chamber. Outside of this chamber a main gas load is provided in the gas generator housing. In case of a crash the propellant is ignited at first which in turn ignites the main gas load which generates the gas flowing into the airbag.
The chamber for the propellant is formed by a cup-shaped sleeve in known gas generator as for instance disclosed in DE 198 12 221 A1. The sleeve is fixed to an ignition device with its open end and the closed end extends into the area of the gas generator housing. The sleeve has lateral breaches which are closed by a film before ignition of the propellant. After ignition of the propellant by the ignition device the film is destroyed by the hot gases of the propellant. The hot gases enter through the breaches into the room with the main gas load and ignite the same whereby the gases flowing into the airbag are generated.
The propellant is mostly present in form of pellets and the main gas load is present in form of tablets. By using a cup-shaped sleeve for the reception of the propellant an elaborate production process is required. Here, at first the pellets of the propellant has to be filled into the cup. Subsequently, the lower part of the gas generator housing with the ignition device has to be fitted onto the cup and has to be connected to the same. Afterwards the lower part has to be rotated around 180° so that the tablets can be filled in.
In order to guarantee good self-ignition properties of the gas generator for instance in case of a vehicle fire it is necessary to burn the main gas load in a controlled manner before its properties are negatively changed by a strong heat reaction. In order to guarantee a safe self-ignition a reproducible and good contact of the advanced ignition substance with the housing wall of the gas generator or sufficient stable heat bridges between the advanced ignition substance and the housing are indispensible. This is not always guaranteed when using a cup-shaped sleeve for the propellant since due to the production and assembly tolerances an air gap between the bottom of the sleeve and the generator housing can be present.